Granted, and before this years AO, I had made my peace that Fed would probably retire with 18 (he was bound to get 1 farewell slam like Sampras), and could possibly be called one of the 3 best players ever (Djokovic and Nadal were close, and Nadal could endanger his slam count).
Then, the AO happened. Then, IW and then, Miami. I am on record on reddit saying that Miami title was hugely important for Fed, when most people were ready to simply be satisfied with even less.
But I guess Fed himself differs. He's smelled blood. 3 straight wins over Nadal go a long way redefining his career; an additional slam was sweeter. Now #19 is in real reach. The slam gap is widening, Djokovic is slumping and may never be what he once was. Nadal is like a candle burning bright before it completely goes off. Seriously, even Nadal may not come back in his 2017 form ever if he fails for the rest of the year (and I fully expect him to fail and not win any significant title).
Who will challenge him for the USO? I cannot see anyone. Also, Fed last won this in 2008. Even Nadal has since 2 USO titles since then!!! This was one of the Fed's best tournaments, and he hasn't won it in almost a decade now. He is due for a USO title too, and it will be a shame if he doesn't take it this year with this insane form.
I might even have understated his title total. If Fed is very smart, plays only the USO, at most 2 MS events (Cincy and one of the indoor ones), and the YEC, he has a real chance to continue with his dominant form in 2018 and take 2 or even 3 slams. Of course, I don't want to overstate too much and jinx it, so I am calling it now - I will be satisfied with my wish list with 22 slams.